Hydraulic transmission for machine tools



l. J. SNADER HYDRAULIC TRANSMISSION FOR MACHINE TOOLS Oct. 6, 1953 6SheetSjSheet l Original Filed Dec. 2, 1937 NVENTOQ Shader fum, 0

@wiwi Oct. 6, 1953y J. sNADER 2,654,291

HYDRAULIC TRANSMISSION FOR MACHINE. TOOLS Original Filed DSC. 2, 1957 5Sheets-Sheet 2 Oct. 6, 1953 l. J. SNADER HYDRAULIC TRANSMISSION FoRMACHINE TooLs 6 Sheets--Shc-z-efI 5 Original Filed Dec. 2, 1937 MMI.

NVENTOL Oct. 6, 1953 J. sNADER 2,554,291

HYDRAULIC TRANSMISSION FOR MACHINE TooLs 5 'sheets-sheet 4 r.. ,I NhfiOriginal Filed Dec. 2, 1957 www O Cf- 5, 1953 l. J. SNADER 2,654,291

HYDRAULIC TRANSMISSION FOR MACHINE TOOLS Original Filed Dec. 2, 1937 6Sheets-Sheet 5 mm Shade/q @al dwg, @la www @df T10@ ya Oct. 6, 1953, 1.J. sNADER HYDRAULIC TRANSMISSION FOR MACHINE TOOLS 6 Sheets-Sheefl 6Original Filed Dec. 2, 1937 NVENTOQ ha SMOG/Q20 MMM/w ma; ein;UITTOQIys-i Patented Oct. 6, 1953 HYDRAULIC TRANSMISSION FOR MACHINETOOLS Ira J'. Snader, Detroit, Mich., assignor to Ex- Cell-OCorporation, Detroit, Mich., a corporation of Michigan ApplicationAugust 3, 1940, Serial No. 351,040, now Patent No. 2,436,406, datedFebruary 24, 1948, which is a division of application Serial No.177,693, December 2, 1937, now Patent No. 2,251,961, dated August 12,1941. `Divided and this application November 25, 1947, Serial No.

1 Claim. (Cl. 90-22) The present invention relates to improvements inhydraulic transmissions for machine tools for performing materialcutting operations, particularly machine tools for grinding screwthreads.

One of the objects of the invention is to provide a hydraulictransmission having a plurality of reversible motors for operating aplurality of machine elements, and control means for simultaneouslysupplying fluid under pressure reversibly thereto.

Another object is to provide an operating mechanism for at least threemovable elements of a machine, including independent hydraulic motorsfor actuating said elements, and control means for supplying motivatingfluid from a common source at different pressures to said motors.

Further objects and advantages will become apparent as the descriptionproceeds.

Figure 1 is a front elevational view of the machine having a hydraulictransmission embodying the features of my invention.

Fig. 2 is a vertical sectional view of the headstock taken along line2-2 of Fig. 1.

Fig. 3 is a fragmentary sectional view taken along line 3 3 of Fig. 2.

Fig. 4 is a fragmentary substantially vertical sectional view takenalong line 4 4 of Fig. 2, and illustrating the mounting and drive forthe headstock spindle.

Fig. 5 is a fragmentary horizontal broken sectional View of the worktable illustrating particularly a taper compensating mechanism.

Fig. 6 is a fragmentary vertical sectional View of the work table, andparticularly the means for supplying pressure fluid thereto.

Fig. 7 is a fragmentary vertical sectional view taken along line 'I-l ofFig. 2.

Fig. 8 is a diagrammatic representation of theV hydraulic circuits forthe machine.

The present application is a division of my copending application SerialNo. 351,040, led August 3, 1940, now Patent No. 2,436,406, datedFebruary 24, 1948, which copending application is in turn a division oforiginal application Serial No. 177,693, iiled December 2, 1937, landnow Patent No. 2,251,961, dated August 12, 1941.

Referring more particularly to the drawings, the hydraulic transmission,constituting the exemplary embodiment of the invention, is incorporatedin aY machine comprising a base I which may be of any suitable form, andwhich preferably is horizontal, with Van elongated front section 2. Thetop of the Vbase section 2 is formed with longitudinal ways on Whch'awork carriage or table 6 is suitably mounted for reciprocation. Aheadstock 1, having a power driven work spindle 8, is mounted on thecarriage 6 for movement therewith, and is pivotally adjustable to adaptthe machine for either cylindrical or taper grinding. A tailstock 9,having a work engaging center I 0 in axial alignment with the spindle 8,may be adjustably mounted on longitudinal ways I l formed on the top ofan elongated frame extension I2 of the headstock 1. The top of the basealso supports a tool ilxture I4 mounted for cross feed and adjustment.The fixture I4 has a power driven spindle I5 which is adapted 'tosupport a suitable grinding element or wheel l5 for operative engagementwith the work, and which is angularly adjustable to compensate for thelead angle of the work thread when grinding screw elements.

The headstock `tubular and of the flange nose end type. Thus,

the outer or operative end of the spindle 8 is provided with a fiange 36formed with an axial locating bore or recess 31 to mount a work fixturesuch as a chuck (not shown). The outer end portion of the spindle boreis tapered to form ak socket 38 for a sleeve 39 into which a work center40 may be removably inserted. An opening 4I in the cover 33 for thecompartment 30 and normally closed by a removable plate 42 allordsaccess to theinner end of the spindle 8 and pei'- mits inserting longwork pieces through the spin- Y dle.

Rigidly mounted within the drive compartment 29 is a motor 43 which inthe present instance is of the rotary hydraulic type. The motor 43 isconnected through step pulleys 44 and 45 and a belt 46 to a transverseWorm shaft 4l journaled in antifriction bearings 48. serves to tensionthe belt 46. A worm 59 on the shaft 4? meshes with a worm wheel 5I fixedon the spindle 8 between the bearings 34 and 35 to complete the rotarydrive transmission.

The elongated headstock 'I is mounted on the y An idler pulley 49provide a peripheral rluicl space.

table e .for pivotal adjustment. about a vertical axis to permit eithercylindrical or taper grinding. More particularly, a tubular pivot sleeve52 is fixed in the bottom of the housing 2B, and.

is swiveled in a sleeve 53 in the table 6. Pivotal adjustment of theheadstock '1 maybe eri'ected by any suitable means operable by a handknob B at the front of the tablet, and .the headstock is adapted to beclamped in `position of :adjustment by suitable gibs 55 and 56 slidablyoverlying the extreme ends.

Fluid under pressure is adapted to be .supplied reversibly to the motor43 through lines '51 and 58. To connect these lines .to the `motor`without necessitating the use of a perishable flexible hose, a manifoldplate 59 (see Figs. 6 and '7) is bolted to the left end of the basesection 2 below the table 6. The plate 59 is formed with three parallelbores `El) opening therethrough longitudinally of the base section 2 toa recess 6| normally closed by a cover t2, and with three lpassages '.63peripherally intersecting the bores. Two of .the passages B3 areconnected respectively to the lines 51 and 58 and the Vthird isconnected to .a

rain line |54. Anchored at 4their outer .ends lwith a `fluid tight sealto the manifold block 59, in communication respectively with the 'bores169, .are three parallel tubes iS5 which lare plugged .or closed attheir inner ends and which extend .freely through three parallel 'bores65 opening longitudinally through an elongated manifold block El on theunderside of the table E.

Each of the tubes A65 is secured to the manifold plate 5B by a bolt G8extending through the associated bore @il into internally 'threadedengagement with the tube and accessible in the recess llil. The bolt 63-is tubular and closed 'at the head end so as to constitute iin effectan extension of the tube 6.5, yand is formed with a plurality of radialports 69 open to the associated passage 53. lThe bore -GS in themanifold block (il is of La larger diameter than the tube B5 to Plainbushings 'lil are xed-in'the bore lili adjacent .the outer endg and havea close sliding litV with the tube E5 to vprovide a guide and a.hydraulic seal. Suitable square wi-re snap rings 'ma are vinserted, intointernal grooves lil-b in the bore .55 lin position to enga-ge the outerends of Athe bushings lll and thereby anchor the 'latter against 'thehigh fluid pressure in the bore between the bushings. Additionalperipheral seals l l are provided in the :ends of the bore es in axiallyspaced relation tothe bushings lil, and coact with `the latter toldeilne small intermediate annular spaces or chambers l2 adapted tocollect vany outwardly leaking fluid. The tube 65 is formed with -radialports '13 which open from the interior thereof to 'the associated boreB5.

The various chambers 'F12 at the ends of the bores 66 are connectedthrough passages '|54 in the manifold block el to one of the bores '68in communication with the drain line 62| so as to provide an outlet forthe leakage of fluid. The other two bores v|56 are in communication withpassages 'l5 opening through the block 6l, the pivot sleeve 52 and thehousing 28, respectively, to opposite sides of the motor R3. It will beevident that the various tubes 55 and the block 61, by reason of theirtelescoping relationship, serve to connect the fluid lines 51 and 5'8and the drain line 64 to the carriage 6 in any position of reciprocationof thelatter, and that the passages in opening through the sleeve 52permit angular adjustment of the headstock without interfering with theconnection of the fluid lines .57 and 58 from the carriage to the motor43.

The table drive Translation of the table 6 is effected through a nut 'itand a lead screw ll which are mounted ior relative rotation, and ofwhich one is fixed to the base section 2 and the other is movable with:the table. 1n the present instance, the nut 16 is supported in anormally xed position in a sleeve 'I8 attached to the base section 2,and the screw il is .supported for a rotary drive on the underside oithe table t. One end oi the screw l1 is freely splined for relativeaxial adjustment in a sleeve 3i rotatably mounted in antifrictionbearings 2 coniined in a lug |33 on the side of the manifold block 61.The sleeve 8| is operatively connected for rotation in timed relation tothe work spindle 8. In the present instance, the drive connectionincludes a gear 8e fixed on the inner end of the spindle B within theAgear compartment 38 of the headstock housing 28. The gear 8d isconnected through suitable change gears 185 'to a shaft 85 journaled 'inthe wall 3|. The change gears 85 are adjustably and removably mounted ona quadrant 8l pivoted on the shaft and ladapted to be clamped to the4wall 3| in position of adjustment by means of a bolt 8S. Bevel gears'89 serve to connect the shaft it to a vertical shaft et extendingdownwardly coaxially through the pivot sleeve 52 and Supported thereinby suitable antifrietion bearings 3|. The lower end of the shaft et isconnected through bevel gears '92 to the sleeve 8|, thereby completingthe drive to the lead screw Ti.

The bottom or" the gear compartment 3B constitutes a reservoir adaptedto contain a lubricant for the gearing therein. An Voil pump 93 ismounted in the bottom of the compartment Se, and is driven 'by a cam 94on the spindle 3. The pump Q3 has an intake Jl below the oil level, andan outlet line '$5 'discharging in the top of the compartment above thegearing.

The right end of the lead screw 'Il ris adjustably anchored in a xedaxial position relative to the table 6. As herein shown, the right endshaft extension of the 'lead screw il extends slidably and Arotatablythrough Aan elongated bearing sleeve 91 `which is secured for axialadjustment in a lug 98 on the underside of the table 6. A backlashcompensating ydevice 'Sii is mounted on the sleeve 91, and takes the endthrust of the lead screw '17.

The backlash device 99 comprises a cylinder Hill which is mounted at oneend on a flange lili on the sleeve 97, and which has connections atopposite ends with pressure fluid supply lines |02 and |83. A piston IElis reciprocable in the cylinder lill), and is connected to the shaftextension of the lead screw Tl. In the present instance, the connectioncomprises a collar secured to the screw Ti, and retained for rotationbetween antifriction end-thrust bearings SBS in the piston |84. .Anadjustment screw lill is threaded through a vtubular extension IDS onthe closed outer end of the cylinder Il, and has a stop |09 on the innerend disposed for engagement by the piston lii to limit the stroke orrange of movement of the latter. The adjustment screw |81 is placedunder 4a frictional tension load to eliminate lost motion by a nut H8threaded thereon within an axial recess in the outer end of the tubularextension Hi8 and urged outby .coil .compression spring means H2.

A hand knob ||3 is ilxed on the outer end oi' the screw |01. Anindicator |01a is mounted on the cylinder I of the device 98 and coactswith a bracket |01b on the lug 98 to facilitate adjustment of the rangeof movement of the piston |04 by means of the screw |01. Hydraulicpressure uid is supplied selectively through one or the other of thelines |02 and |03 to shift the screw 11 relatively to the table 0 andthereby compensates for the total backlash. Upon reversing the table 6,the take-up on the screw 11 is also reversed to move the table ahead inthe new direction of travel an adjustable extent corresponding to thebacklash so that the cutting4 path of the grinding wheel I0 will beexactly the same in both directions of table movement.

Since the backlash device 99 is an auxiliary mounted on the table 6, thelines |02 and |03 to the cylinder |04 are connected through the manifoldblock 61 in the same manner as the lines 51 and 58 to the spindle motor43. Thus, the block 61 is formed with two longitudinal bores 4 connectedthrough passages ||5 respectively to opposite ends of the cylinder |04.Two tubes ||6 are relatively reciprocable in guide bushings ||1 andseals ||8 in the outer ends of the bores ||4, and are formed with radialports ||9 intermediate their ends. Leakage chambers |20 between thebushings ||1 and seals I8 are connected through passages 2| to the drainbore 66. The xed ends of the tubes ||6 are connected to the manifoldplate 59 by means of bolts |22 which extend through bores |23 in theplate and which have radial ports |24 open to passages |25 intersectingthe bores and connectedrespectively to the lines |02 and |03.

Hydraulic operating system Fluid under pressure is adapted to besup-plied by a variable delivery pump 403 having `a discharge line 404and an intake line 405 opening from a sump 406 within the base The pump403 may be of any suitable character, and preferably is of the orificepressure controlled type disclosed in Patent No. 2,299,234, issuedOctober 20, 1942, to Ira J. Snader and Max A. Mathys. More particularly,the pump 403 has a control line 401 which, as hereinafter described, isadapted to be connected by a valve 408 either to the exhaust side of thehydraulic system for utilization of a pressure built up by a ilowrestriction to cause the delivery of iluid in variable amounts asrequired and at a predetermined substantially constant pressure withoutthe use of relief valves, or to the pressure discharge line 404 tosubstantially stop fluid delivery except 'as required to maintain saidpressure. The pump 403 may be driven by any suitable means, such as anelectric motor 4| 0 connected thereto through a -drive coupling 400, andcontrolled by start and stop buttons 4|| anda master stop button 4|2 forthe entire machine on the front of the machine base To prevent thetransmission of vibration,fthe pump 403 and the motor 4|0 are 'mountedon a base 4 I3 resiliently supported as by rubber on the floor adjacentthe base The pressure line 404 opens to a main hydraulic control panel4| 6 on the front ofthe base section 2. The hydraulic panel issectionally constructed of castings and grooved plates housing thevarious control valves and defining the connecting passages in a compactarrangement.

A suitable direction and stop valve 4|1 is operable to connect thepressure line 404 selectively to either of the lines 51 and 58 leadingto the motor 43 for driving the table 6 and the work spindle 8, andsimultaneously to connect the other of said motor lines to an exhaustline 4|8 discharging to the sump 406.

In its preferred form, the valve 4|1 comprises a tubular bushing 4|9 xedin a bore 420 in the panel 4|6, and having formed therein inlongitudinally spaced relation two pressure ports 42| and 422 of whichthe port 42| is connected to the line 404, two motor supply ports 423and 424 between the pressure ports and connected respectively to thelines 51 and l58, and a central exhaust port 425 between the supplyports and connected to theexhaust line 4| 8. A valve piston 426 of thespool type is reciprocable in the bushing 4|9, and is formed with threelongitudinally spacedperipheral grooves or recesses 421, 428 and 429.The central recess 428 is always open to the exhaust port 425, and theend recesses 421 and 429 are interconnected through an axial bore 430 inthe piston 426 and are always open to the pressure ports 42| and 422. Itwill be evident that in one end position of the valve piston 426, thelines 51 and 58 will be connected respectively to the pressure andexhaust lines 404 and 4|8 to operate the motor 43 in one direction, andin the other end position, the connections will be reversed to operatethe motor in the opposite direction. In the central or neutral position,both lines 151 and 58 will be disconnected from the pressure line 404and connected to the exhaust line 4 I8.

Suitable flow restriction means is interposed in the exhaust line 4|8 tocontrol the rate of drive by the motor 43 in either direction. In thepresent instance, this means consists of threeadjustable restrictionorifice valves 43| 432 and 433 located respectively in three parallelbranch lines 434, 435 and 436, and adapted for selective connection inthe exhaust line 4|8 by a three position valve 431. These orifice valvesare independently adjustable from the front of the panel 4|0. In thepresent instance, the orice valve 432 in the intermediate branch line435 is adjusted to provide a relatively large flow area adapted toeffect a rapid traverse, and the other orice valves 43| and 433 areadjusted to provide relatively small flow areas adapted to effect slowdrive speeds or feeds.

The orifice selection valve 431 comprises a bushing sleeve 438 fixed ina bore 439 in the panel 4|5. Four longitudinally spaced ports 440, 44|,442 and 443 are formed in the sleeve 438 and open respectively to thelines y434, 435, 438 and 4 8. A valve piston 444 is reciprocable in thesleeve 438, and is formed with two longitudinally spaced sets of ports445 and 44S interconnected by an axial bore 441. The arrangement is suchthat the ports 44| and 446 are connected to institute rapid traversewhen the piston 444 is in central position, the ports 440 and 445 areconnected to institute a slow feed when the piston is in one endposition, and the ports 442 and 446 are connected to institute a secondslow feed when the piston is in the other end position.

The operation ofthe valves 4|1 and431 is under the control of aplurality of pilot valves consisting of a start and stop valve 448,direction control valves 449 and 450, and speed control valves 45| and`452. These pilot valves are located in a panel 4| 5, and are includedin pilot control circuits under a relatively low operating pressure.

l Fluid is supplied from the main pressure line 404 to a pilot pressureline -453 under the control actueel fof .anautomatic regulating.valve-45.4. valve .comprises va bore455 .opening centrally to .ahlenpressure .chamber .4,55 .connected to .the .line .49.4, and at oppositeends :respectively .to a low pressure .chamber 45.1 connected to the.line 4.53 and an .exhaust chamber 45.8 connected to .an .auxillaryexhaust line 45B leading to the sump 458. A plunger 4.60 extendsslidahly through the bore I455, and lis .urged endwise .against .thepressure in the .chamber 451 .by .a .compression spring .4.5i seatedagainst an ,adjusting .screw .4.62 in .the exhaust .chamber 455. Theplunger .4.6.0 is formed with a longitudinal ybore 483 open to the lowpressurechamber14,57., and .adapted for .communi- ,cation with .the.chamber 45.5 .or the `.chamber 45,8. when the pressure in the 4chamber45T! is .too low, replenishing v.fluid will be .supplied ,from thechamber 455 through the .bore 4&3. When the ypressure is at .the`desired value determined hy the `spring 4.6i, the bore 453 will beclosed to cut .on the now of .illlid- In the .event of high pressureleakage,

the resulting excess lrn'essure will he bypassed to .the exhaust chamber,4.5.5. As a result, ia balanced relatively .low zconstant pressure issubstantially maintained inthe line 4.53 at .all times.

The .direction valve 4H is movable into .stop position by two centeringplungers or vcollars A41,54 which `are ,freely reciprocable in cylinders4,65 vat opposite ends of the bore428 for engagement with opposite ends.of .the valve piston .426. The outer ends .of the cylinders 465 areopen to a line 458 adapted for connection by the pilot valve 448 eitherto the .pressure vline 453 or the exhaust line .4.59.

The Start and stop pilot valve 448 comprises a valve bore 48'! formedyin Aand opening to the top .of the panel 4l 5. A differential valveplunger 468 `is reciprocable in the bore 461, and 'has an actuating stem45.9 projecting outwardly .for engagement .by a stop .dos 478`adiustahly mounted kon .the table 6, The bore 461 has suitable portconnections with thelnes 459 and 455, and is always .onen .at the smallend of the plunger 46.9 to the pressure 'line .45.3. The bore 48'! isalso open at the large end of the plunger 459 to a line 4'H adapted tobe connected by a hand valve .412 4either .to the pressure line 45.3 .orthe exhaust .line 459. The .hand valve 412 comprises a dijiferentialcylinder 455 connected at the large .and

small ends respectively to the `lines 465 and ,459, u

.and having suitable port connections in one side with the lines 45.3and dll. A d nerential valve .piston .474 is reciprocable in thecylinder '413 by a hand lever 415.

To institute operation, the valve piston 414 is moved into position tolconnect .the lines 453 and 41,1.. Thereupon, the valve plunger 468 iselevate@- 'bv differential pressure, and connects the 'lines 459 and 465to release the direction valve 4V! for adjustment into either endposition. Upon lowering the plunger 488 either by the dog 14.1.8 orthrough actuation of the hand valve 412 to exhaust the Aline 4H,pressure fluid is supplied .to the line 4% to center ,the directionvalve 4H and .to Vmove or hold the hand valve 472 in stop position.

The direction valve 4H Vis reversible "by two pins or plungers 455adapted to act against the opposite ends of the valve vpiston 426. Oneof the reversing plungers 416 is reoiprocable in a cylinder 4l?connected to a nuidsupplyline 418, .and extends axially through theadjacent centering collar 464. The other plunger 416 is reciprocable ina .cylinder 419 formed in the other centering .collar 464, and connectedthrough a peripheral port 48!) in .the latter to a luidsupply line 48LThe .lines A,.418 and 48| `are adapted to 'be connested through a rotary.hand valve 482 to two lines 483 Land `48.4 controlled by .the direction.pilot valves 449 .and ,458, The valve 482 is adjustable to reversethese connections for the grinding of left hand .threads so that thespindle drive .will properly conform to the lead screw rotation as.controlled by the change gearing 85.

The pilot valves .449 and 458 respectively comprise .two vertical bores485 and 48.5 formed in and .opening to the top of the panel 415, and twospool valve plungers 4 81 and 488 reciprocable therein and having axialstems 489 vand 498 pro- .Jeting therefrom for selective engagement bydogs '4,91 and 492 adjustably mounted on the'tahle l. The pressure line.453 opens to the upper ends oi the bores 485 and 485, .and the pressurefluid therefrom acts `Aagainst the relatively .small upper piston areasof the plungers 481 and 438. The `bores 485 and '486 also-have portconnections with the exhaust line 458 .and respectively with the lines4- 84 and 483. The latter also open respectively to the lower ends ofthe bores 485 and 488 to provide cross connections so that the pilotvalves 44.9 and 450 will reset each other alternately in operativeposition for respective coaction with the dogs 49| and 492.

The port connections are such that when the plunger 489 is depressed,the cross line 484 will be connected to the pressure line 453, therebycausing upward movement of the plunger 499 .to connect the other crossline 483 to the exhaust line 4:59. As a result, the Aplunger 489 islocked in depressed position, the plunger 490 is held in elevatedposition, and one directional pin 415 is actuated to move the direction`valve 4H into position to institute carriage movement to the left.Conversely, when the plunger 490 is depressed, the .lines 483 and 484are connected respectively to the pressure and exhaust lines 453 and 459to .reverse the valve 4H and institute carriage movement to .the right.Adjustment of the hand valve 432 vfor grinding left hand threads J willyreverse the motor 43 and hence .the rotation o f the work spindle 8 inrelation to the pilot valve control, hut the directional control of thetable B is left unchanged by suitable changes in the gearing B5 in thelead .Screw drive.

The direction pilot valves 449 and 458 may be reversed at any timeindependently of the dogs 491 and 492 by means o f a hand valve 493. Tothis end, two lifting pistons 494 and 495 are mounted 'in cylinders 49.6.and 49'! at the lower ends .or thebores 4&5 and 486, and normally con-.stitutestops for the plungers 4.87! and 488. However, either of thesepistons .49.4 and 495 may be actuated hydraulically to elevate theassociated pilot plunger vinto operative position. The hand valve 493comprises a bore 498 having port connections with the pressure andexhaust lines 453 and 458 and lwith two lines .499 and 588 openingrespectively to the lower ends of the lifting cylinders 498 and 491. Avalve piston 581 of the spool type -is normally held by spring means 582in central position to connect both of the lines 495 and 585 to theexhaust line 459. Movement of the valve piston 5M into opposite endpositions serves to connect the lines 493 and 58D respectively andreversibly to the lines 453 and 459 to supply pressure iluid selectivelyto one or the other ofthe cylinders 495 and 497.

The orifice selection valve 45'? is controlled 'by the rapid traversepilot valve 452 and the feedpilot Valve 45| in conjunction with thedirection pilot valves 449 and 450.

Two centering collars or pistons 503 and 504 are reciprocable incylinders 505 and 506 at opposite ends of the bore 439 for engagementsimultaneously with opposite ends of the valve piston 444. The outerends of the cylinders 505 and 506 are open in parallel to a line 501adapted for connection by the rapid traverse valve 452 either' to thepressure line 453 or the exhaust -line 459. The valve 452 in turn iscontrolled by the feed valve 45|. These -valves 45| and 452 respectivelycomprise vertical bores 508 and 509 formed in and opening to the top ofthe panel 4|5, and spool type valve plungers 5|0 and 5|! reciprocabletherein and having stems 5|2 and `5|3 projecting therefrom for selectiveactuation by dogs 5|4 and 5|5 adjustably mounted on the table 5. Bothbores 508 and 509 are open at the upper end above the small pistcn areasof the plungers 5|0 and 5|| to the pressure line 453 and have portconnections with the exhaust line 459. The bore 505 also has a portconnectionwith the line 501 which has a cross connection with the lowerend of the bore 508 beicw the large piston area of the plunger 5F15.Likewise the bore 508 has a port connection with a cross line 5|4aopening to the lower end of the bore 509 below the large piston area ofthe plunger 5| I.

The port connections are such that when the plunger 5H is depressedpressure iiuid is supplied frcm the line 453 to the line 501 to elevatethe plunger 5 0 and center the valve 43'?. At the same time, the plunger5|0 connects ythe cross line 5|4a to the exhaust line 453 to lock thevalve 5|3 in its lower position. Fluid from the motor 43 is nowexhausted through the rapid traverse orice 432. When the feed plunger5|0 is depressed, pressure luid is supplied from the line 453 to thecross line 5|4a to elevate the plunger 5|| which thereupon connects theline 501 to the exhaust line 459 to relieve the cylinders 505 and 506and the lower end of the bore 508.

When the feed plunger 5|0 is depressed, the valve 431 is selectivelyadjustable automatically into opposite end positions as determined bythe direction of carriage travel under the control of the directionpilot valves 449 and 450. Thus, two adjusting pistons Elia and 5|6 arereciprocable in cylinders 5|1 and 5|8 at opposite ends of the valve bore439 and extend slidably through the centering pistons 503 and 504 forengagement respectively with opposite ends of the valve piston 444. Theouter ends of the cylinders 5|1 and 5|8 are connected respectively tothe linesr 483 and 494. It will be evident that when the plunger 488 isdepressed to institute carriage movement to the right, pressure fluid issupplied to the cylinder 5|1 to connect the feed orifice 433 in theexhaust line 459. Alternatively, when the plunger 481 is depressed toinstitute carriage movement to the left, the feed orifice 43| isconnected in the exhaust line 459. The oriiice valves 43| and 433 may berelatively adjusted to obtain the same or different rates oi -drive inopposite directions of carriage travel.

The table dogs may be selected and mounted to obtain diierent cycles ofoperation. The position of the reversing dogs 49| and 492 determines thelocation and extent of the range of table reciprocation. The stop dog410 is of the pivotal gravity type and adapted to depress the stem 469only upon movement of the table 5 in one direction. To stop the table inthe opposite direction, it is merely necessary to reverse the dog 410 onthe pivotal mounting. After depressing the stem 469, the dog 410 willswing past the latter to permit institution of the next cycle. In thearrangement as shown, if the direction dog 49| is adapted to engage thestem 489 before the dog 410 can engage the stem 469, the tablereciprocation will be continuous. Conversely, if the dog 410 is adaptedto engage the stem 453 before the direction dog 49| can engage the stem489, the table 6 will come to a stop at the end of the right-handmovement.

Each of the speed'control dogs 5|4 and 5|5 is also operable only uponmovement of the table in one direction. As shown, the feed `dog 5|4 isfreely pivotal to the left and is, therefore, adapted to drag freelyover the stem 5|2 upon movement of the table to the right and to depressthe stern only upon movement to the left. To institute feed during tablemovement to the right, it is merely necessary to reverse the dog 5|4 onthe pivotal mounting. The rapid traverse dog 5| 5 is adapted to depressthe stem 5|3 upon movement of the table to the right but is ineffectivein the opposite direction of movement. It will be understood that anydesired number of dogs 5|4 and 5|5 elective in either direction may beprovided depending on the particular series of rapid traverse and feedmovements to be obtained.

The pump control valve 408 is operable synchronously with the directionvalve 4|1 under the control of the start and stop pilot Valve 440. Thisvalve 408 comprises a bore 5|5 open at one end to the adjacent cylinder465 and at the other end to the exhaust line 453, and having portconnections with the pressure line 453, the pump control line 401 and aline 520 branching from the exhaust line 4|8 ahead of the orificeselection valve 431. A differential valve piston assembly 52| isreciprocable in the bore 5 9. When pressure iiuid is supplied to thecylinders 455 to center the valve 4|1 in stop position, it also acts onthe large piston area of the assembly 52| to connect the motor controlline 401 to the high pressure line 404 and thereby reduces the deliveryof the pump to maintain a low pilot pressure in the system. When theadjacent cylinder 465 is exhausted, pressure iiuid from the line 453acts on the small piston area vor the plunger 52| to connect the controlline 401 tothe or1iice pressure line 520. 'I'he pressure set up in theexhaust line 4|8 by the selected orifice valve now controls the pump 403to obtain a variable dellvery as required at a constant predeterminedpressure.

It-will be seen that the main valves 4|? and 431 and the various pilotvalves 448, 449, 450,` 45| and 452 are controlled and operated by therelatively low pilot pressure. As a result, the relatively high pumppressure can be confined to one valve block, and the remaining valveports can be made relatively light Without the likelihood of leakage.

Various auxiliary elements of the machine are operated by auxiliarycircuits including a relat1vely low pressure line 522 adapted to receivepressure fluid from the main pressure line 454 under the control of anautomatic regulating valve 523. This valve 523 comprises a bore 524opening from the chamber 456 at opposite ends to the exhaust chamber 458and a chamber 525 connected to the line 522. A plunger 525 isreciprocable in the bore 524 and is urged against the pressure in thechamber by a compression spring 521 seated against an adjusting screw528.

was

The plunger has an axial'` bore 52'9 open to the chamber 525 and adaptedfor communication with the chamber 456 to supply pressure fluid up to apredetermined low pressure or for communication with the chamber 458` torelieve excess pressure fluid to the exhaust. The valve 523 operates inthe same manner as the valve 454 to maintain a constant relatively lowpressure in the line 522.

The backlash cylinder for the table feed screw 11 is connected by thelines |02 and |03, and is adapted to be reversibly connected by a valve533 to the pressure and exhaust lines 522 and 459. The valve 533 isautomatically reversible with the direction valve 4|1 under the controlof the pilot valves449 and 450 so that the backlash will be taken up ina direction corresponding to the table movement once for each reversalof the tablet. Thus, the valve533 com-A prises a bore 534 openv atopposite ends to the lines 483 and 484, and a spool type valve piston535 reciprocable therein. In one position of the piston 535, the line|02 is connected to the pressure line 522, and the line |03V isconnected to the exhaust line 459, and in the other position, theconnections are reversed.

Operation The operation of themachinewill be apparent from the foregoingdescription, and briefly summarized is as follows:

The work to be ground is attached to the. work spindle 8. Then, thehandvalve- 482, andhence the valve 4H, is adjusted, to obtain thedesired direction of spindle rotatiOIl, and suitable changev gears 85are used to correlate the translation of the table 6 both in rate anddirection, tothe spindle rotation so ask to describe the desired threadlead. j 1 j The switch 4|I is actuated to start the. motor 4|0,l and thelever, 415 is actuatedV to institute` operation of the table and thespindle 8.t The table 5 will now be translated automatically throughapredetermined` cycle which may cornprise any desired program of rapidtraverse and feed movements. At any point in the; cycle, the directionmay be reversed by/actuating the hand valve 493. The rapid traverse rateis determined by the exhaust oriiice 432, and the feed rates in oppositedirections l are controlled respectivelyA by the orices 43| and. 433.independently adjustable.

These orifices are operation may be discontinued atA any timebyactuating the hand lever 415.

The reciprocation of;V the table 5 may be continuous or interrupted de-A pending on the location of the stop dog 410. The

At each reversal' ofthe table 6, any existing:

backlash in the table drive is automaticallycompensated for by thedevice 39. I claim as my invention:

s Ina` machine tool havingv a drive backlash compensator, thecombination of a base, guidek means fixed to said base, a slidablemember. mounted on said guide means for translationall ymovementtherealong, a drive for said slidable member including a lead screwelement andA a nut element, one of said elements being iixed relative tosaid base, the other of said elements being connected to said slidablemember for .movement therewith, a rst hydraulic motor drivinglyconnected to one ofv said elements for rotating the same, a secondhydraulic motorV connected for the effecting of backlash compensatingmovement of' one of said elements rela- ,.tive to said other element andsaid slidable memggfber and said base, pump means for supplying a;

source of fluid at high pressure, means includ ing a first adjustablevalve connecting said high pressure source with said iirst hydraulicmotor,A .a iirst pressure reducing valve connected with *said pump meansfor supplying fluid at reduced pressure to said second hydraulic motor,means including a second adjustable valve connecting said secondhydraulic motor with the reduced pressure side of said iirst reducingvalve, pilot "'valve means interconnected with said first and secondadjustable valve means for controlling both said latter means, and asecond pressure reducing valve connected with said pump meansforsupplying iiuid at reduced pressure to said pilot valve means.

IRA J. SNADER.

References Cited in the ille of this patent UNITED STATES PATENTS NumberName Date 1,723,852 Haas Aug. 6, 1929 1,850,392 Haas Mar. 22, 19321,896,052 Ferris Jan. 31, 1933 1,899,654 Ward Feb. 28, 1933k 1,965,221DeHaas July 3,` 1934 2,002,924 Romaine etal. May 28, 1935 2,037,262Parsons Apr. 1.4, 1936 2,061,778 Schicht i.- Nov. 24, 1936 2,070,807Roehm et al Feb. 16, 1937 2,196,231 Ridgway Apr. 9, 1940 2,267,177'IWyman' Dec. 23, 1941 2,391,487 Shader Dec. 25, 1945 ft2 2,436,406Shader Feb. 24, 1948.

